A near-distance wireless communication network configured by a sensor device which acquires biometric information and a gateway device which collects pieces of biometric information from the sensor device and transmits the biometric information to another network, is called a body area network (BAN). With utilization of this BAN, it is feasible to realize an application which improves the efficiency of an inspection at a medical institution or enriches health management outside the medical institution by measuring the biometric information such as heart beats and a body temperature at all times.
As communication methods used for the BAN system, there exist a method of utilizing electromagnetic waves propagated in the air spaced away from the living body, a method of using the electromagnetic waves propagated along the surface of the living body, and so on.
In the wireless communication system which uses a spatial transmission path as in the BAN, there is a case where a human body as an obstacle might largely affect a wireless environment. Such being the case, some methods for avoiding this problem are disclosed (refer to Patent documents 1 through 4 given below).    [Patent document 1] Japanese Laid-open Patent Publication No. 2002-100917    [Patent document 2] Japanese Laid-open Patent Publication No. 2001-102844    [Patent document 3] Japanese Laid-open Patent Publication No. 2002-185391    [Patent document 4] Japanese Laid-open Patent Publication No. 2007-78482